Jens Lemanski

From the mid-1600s to the beginning of the eighteenth century, there were two main circles of German scholars which focused extensively on diagrammatic reasoning and representation in logic. The first circle was formed around Erhard Weigel in Jena and consists primarily of Johann Christoph Sturm and Gottfried Wilhelm Leibniz; the second circle developed around Christian Weise in Zittau, with the support of his students, particularly Samuel Grosser and Johann Christian Lange. Each of these scholars developed an original form of using geometric diagrams in logic. In this paper, I will trace the historical notes of John Venn and other modern logicians back to the original works published in the Weigel and Weise circles and describe the development of using geometric figures for logical reasoning and representation in that period of time.

Normally in nowadays philosophical research the term 'Neoplatonism' is coined and it was used the first time by Jacob Brucker in the first half of the 18th century. But there are signs that the concept is much older. So this essay follows the trace of the term 'Neoplatonism' from german philosophical historians, like Büsching and Brucker, back to the Cambridge Platonists and tries to demonstrate that the origin of the concept is based on some texts of the late antiquity which act first on the research of the early modern philosophy.

The paper distinguishes three interpretations of Kant’s so called ‘Copernican Revolution’: an epistemological, a hermeneutical and a scientific-theoretical or methodological one. It is argued that the ‘scientific-theoretical reading’ can be based on new historical evidence. Kant borrowed the metaphors ‘army of stars’ (‘Sternenheer’) and ‘spectator’ (‘Zuschauer’) from Johann Heinrich Lambert and used them in a context similar to Lambert’s. This suggests that Kant’s formula “first thoughts of Copernicus” (“den ersten Gedanken des Copernicus”) refers, again following Lambert, to the first 9 chapters of Copernicus’ De revolutionibus, which contain a change from inductive geocentrism to deductive heliocentrism. This interpretation is itself no revolution: Johann Baptist Schad claimed in 1800 that metaphysics must be regarded as a deductive rather than an inductive science. Kant explicitly agreed.

In the second preface to the Critique of Pure Reason, Kant claims that Galileo Galilei, Evangelista Torricelli and Georg Ernst Stahl caused a scientific revolution in experimental physics (B xii). In this paper, I advance the historical thesis that Kantʼs claim refers precisely to three passages from Discursus et demonstrationes mathematicae (Galilei), Lettera a Filaleti Di Timauro Antiate (Torricelli), and Beweiß von den Saltzen (Stahl). This historical thesis provides evidence for a newer systematic interpretation, which says that the topic of the second preface is not epistemological, but rather methodological.